2bbl to 4bbl on 289
01-11-2017, 10:13 PM
#1
Thread Starter
Join Date: Aug 2016
Location: Arkansas
Posts: 6
2bbl to 4bbl on 289
Ok guys, I have a 1968 Mustang with a freshly rebuilt 289. Problem is, it has a 2bbl carb and produces crappy power. I want to upgrade to a 4bbl carb. My questions are 1. Do i need to replace valves?...2. Suggestions on carb size and manufacturer? 3. Intake preferences? 4. Since I am already back into the engine, I'd like to add a mild cam for hole shots. Nothing drastic...just a better hole shot. Suggestions on cam size (lift/duration etc) and what else i gotta replace if I go up in cam size? This car is a show winner but a turd coming off stop lights against some chick in a Prius......lol 
01-12-2017, 07:55 AM
#2
1st Gear Member
Join Date: Aug 2013
Location: Texas
Posts: 113
If you want to keep it fairly simple then just get a new intake manifold (this Edelbrock is a good one https://www.summitracing.com/parts/edl-21213) and a 650cfm holley carb (Edelbrock carb would work also but I prefer holley).
If you want to go deeper then the next thing I would do is get headers and exhaust. This stuff can be done without taking the entire engine apart so I'd start there.
Do you know what your differential ratio is? That can make a huge difference.
If you want to go deeper then the next thing I would do is get headers and exhaust. This stuff can be done without taking the entire engine apart so I'd start there.
Do you know what your differential ratio is? That can make a huge difference.
01-12-2017, 06:24 PM
#4
6th Gear Member
Join Date: Aug 2007
Location: Elk Grove, CA
Posts: 5,896
Changing out the intake, carb, and cam may net you some improved power/torque, but I suspect you'll still be disappointed.
Sounds to me like you might want to be looking at re-gearing the rear end. Factory gearing is often 2.79:1, which is terrible for any kind of performance.
In switching from 2.79:1 to 3.25:1 gearing in my '67, I felt more seat-of-the-pants difference than I did from changing from a tired 289 to a fresh 331.
Sounds to me like you might want to be looking at re-gearing the rear end. Factory gearing is often 2.79:1, which is terrible for any kind of performance.
In switching from 2.79:1 to 3.25:1 gearing in my '67, I felt more seat-of-the-pants difference than I did from changing from a tired 289 to a fresh 331.
01-12-2017, 07:15 PM
#5
2nd Gear Member
Join Date: Feb 2016
Location: MT
Posts: 276
Edelbrock offers matched kits that combine intake, carb and cam so everything works well together. Plan on a good dual exhaust too as you can't improve the intake side of an engine without addressing the exhaust. Gears are a good suggestion too.
01-12-2017, 08:54 PM
#6
1st Gear Member
Join Date: Aug 2013
Location: Texas
Posts: 113
A couple of words of caution
1. If you change your cam too much then you may also need to change your torque converter.
2. How is your cooling? If you are going to heat things up you'd better be able to cool then down.
3. How are your brakes? Going fast is fun but being able to stop is more important. If you are still on factory drums then change them!
1. If you change your cam too much then you may also need to change your torque converter.
2. How is your cooling? If you are going to heat things up you'd better be able to cool then down.
3. How are your brakes? Going fast is fun but being able to stop is more important. If you are still on factory drums then change them!